SACRAMENTO — Federal prosecutors announced a statewide auto insurance fraud crackdown Thursday, charging key figures in an alleged multimillion-dollar kickback scheme involving several legal offices and more than 100 chiropractors, about half of them in Los Angeles.

Following a nine-month investigation, the U.S. attorney's office here charged four attorneys, two law office administrators and a Hollywood chiropractor who administered a network of clinics with defrauding the lawyers' clients and insurance companies of nearly $18 million.

U.S. Atty. Charles J. Stevens said the probe has identified at least 175 other suspects and that more charges will follow.

Stevens urged "cheaters to come in from the cold" and said: "We find everybody who has done this. We will prosecute them, and those who don't cooperate with us will spend a significant period of time in jail."

In a novel approach to battling insurance fraud, a task force of federal and state investigators, assisted by several insurance companies, targeted the collusion of lawyers and medical providers in defrauding both insurers and their clients through a system of kickbacks and inflated medical billings.

Even though many of the auto injury claims may have been fraudulent, Stevens said investigators nonetheless ignored the possible culpability of claimants, treating them instead as victims "sold out by their attorneys." The prosecution will focus solely on the flow of money between the lawyers, the doctors and so-called cappers--agents who charge fees to deliver accident victims to lawyers.

The schemes that prosecutors described Thursday used methods similar to ones that authorities have been uncovering for years in Los Angeles and other big cities. However, the current probe disclosed a level of refinement, an audacity and a scope that is rarely seen, investigators said.

For example, they said, specialized squads of cappers were used to recruit accident victims from different ethnic groups, including Russians, Filipinos, Southeast Asians and Latin Americans of various nationalities.

Banayan, who had more than 100 chiropractors under contract statewide, received $2 million in insurance payments from the Beverly Hills law firm of Baumann & Rose but returned $1 million to the law firm as kickbacks, the charges state. He allegedly forged the signatures of Baumann & Rose clients to whom the insurance checks were made out, and then cashed the checks at check-cashing facilities.

After that, Stevens said, Banayan would "throw the cash into a sack and walk it back to the attorneys."

Most of the medical center kickbacks and nearly all of the lawyers' payments to cappers were in cash, authorities said. Sometimes at Baumann & Rose, "cappers would be lined up in the lobby waiting for payments," one of the prosecutors said. Eventually, he added, the firm became safety-conscious and doled out the money from a blue safe in one of the lawyers' offices.

The principal of Baumann & Rose, Stanley J. Baumann, was charged Thursday with one count of mail fraud.

Baumann's brother Aaron Baumann, administrator of the law firm, and Aaron Baumann's wife, Jane Baumann, were both charged with one count each of mail fraud and tax fraud.

Stevens said Banayan's company, Maimonides Health Center, also paid other lawyers for referrals. He said that the Baumann & Rose firm had received at least $12.5 million more in kickbacks from other, unnamed medical providers.

Also charged with mail fraud were Monroe Zalkin of Miami, who is alleged to have run the Baumann & Rose office in San Diego, and E. Andrews Matyas of Beverly Hills.

Monroe was also charged with one count of tax fraud and Matyas with one count of filing a false report on the amounts of money paid to medical providers.

A fourth lawyer, Thomas Patterson of Santa Ana, who was charged in June, pleaded guilty Thursday to one count of mail fraud and was cooperating in the investigation, said Assistant U.S. Atty. Daniel S. Linhardt, who is handling the case.

In some instances, prosecutors said, the schemes were set up by law office administrators who bought the use of a lawyer's name to milk insurance companies.

In entering his guilty plea Thursday before U.S. District Judge David F. Levi, Patterson said he hired an administrator to run his office and later discovered that the administrator was receiving kickbacks from Banayan.

Patterson said he eventually put a stop to the practice, but had allowed the improper use of his name to continue for about 18 months.

Stevens said he could give no information on possible plea agreements in the cases filed Thursday, but said that the U.S. attorney's office typically files charges, rather than seeks indictments, when a plea is likely.